A spillway or an overflow structure will be provided to discharge 125 percent of 25-year storm runoff without flooding upstream development. Detention basin outflow shall not be allowed to run uncontrolled over a pedestrian facility or sidewalk. This does not apply to emergency overflow provisions.

Entrance facilities shall be designed for the 25-year storm developed conditions except for sump conditions in which case the design will be for the 50-year storm developed condition.

Nuisance Water shall not be introduced into a retention or a detention basin. A gutter or bypass flow device shall be installed to ensure that any nuisance water which bypasses drywells will also bypass detention, retention, and retarding basins. Development must mitigate all nuisance water developed on site.

All detention basins shall incorporate a gravity drain of sufficient size or capacity to drain the detention basin dry (no water in the basin) within 24 hours, once runoff to the basin ceases.

Retarding basins, because of their retention feature, will be subject to the same percolation criteria as retention basins. That is, they shall percolate dry within seven (7) days. If this is not possible, the City Engineer on a case-by-case basis may allow a pumping system to meet this criteria.

All weirs, orifices, spillways, underdrains, and other control or design features which are subject to malfunction due to collection of trash or debris shall be protected, and the design of such features shall be clearly and adequately shown on the drawings of the detention basins